Joe Sullivan wrote: "...The challenge is the compound angle. I'll be joining
four faces that are tapering. The closest I have come to this is in coopering,
but with that I felt my way into the angles with a paper pattern and a sliding
T-bevel, and it was a single angle throughout, with no taper. Here, I don't
know where to start...."
Kerf it in. I think that's the proper term for shipbuilding, making tight
threshing floors, etc. Rough-cut the boards, rough-plane them, then run a saw
down the horribly open, gappy joints. Repeat until you get a tight fit. For your
lamp you might clamp the four sides together, then saw down two diagonally
opposed joints at once. Alternate one diagonal and the other diagonal. You can
adjust and correct the tapers as you go along. Sneak up on the final shape.
Trying to do this with numbers is just going to screw you up. Rely on your tools
and your eye, do it the easy, simple, neo-traditional way.